Preparation

Unfold pastry sheet and cut a 3-inch square from pastry with a sharp knife (reserve remaining pastry for another use).

Bake pastry square on an ungreased baking sheet until golden brown, 15 to 20 minutes. Transfer pastry to a rack and cool completely, then cut pastry horizontally into 2 layers. Stir together crème fraîche and granulated sugar until sugar is dissolved.

Just before serving, put bottom half of pastry on a plate and top with crème fraîche and raspberries, letting some berries spill onto plate. Cover with top half of pastry and dust with confectioners sugar.